An image forming apparatus such as a multi-function peripheral is provided with a fixing device for fixing a toner image on a paper. In the fixing device, for example, a temperature of a heater or a fixing belt of the fixing device, by which the paper is heated, is measured using a temperature measuring element such as a thermistor or a thermopile.
A fixing device included in a recent image forming apparatus is provided with a heater of which heating unit is divided in a direction orthogonal to a paper conveying direction in the fixing device and which is capable of suppressing power consumption when heating a paper by selectively heating the divided heating unit according to a paper size. Therefore, when measuring the temperature for each heating unit, a plurality of temperature measuring elements are required.